The study involves the novel use of microdialysis in human skeletal muscle and adipose tissue. Early observations determined that concentration gradients exist between extracellular fluid (ECF) and intravascular compartments for substrates and the high levels of glycerol (marker of lipolysis) seen in skeletal muscle indicated the presence of high rates of intramuscular lipolysis, a hitherto unrecognized metabolic phenomenon. We plan to study in more detail the role of intramuscular lipolysis in insulin resistance of diabetes.